Wisconsin Gov. Scott Walker

Prosecutors believe Wisconsin Gov. Scott Walker, a potential 2016 Republican candidate for president, was at the center of a nationwide "criminal scheme" to illegally coordinate fundraising with outside conservative groups, according to previously secret court documents released Thursday.

The documents were filed as part of an ongoing lawsuit challenging the probe by the conservative group Wisconsin Club for Growth. They were ordered publicly released Thursday by a federal appeals court judge after prosecutors and the Wisconsin Club for Growth did not object. (AP)